Renewable electric fuse



Nov. 3,1925. 1,559,890

F. C. LA MAR RENEWABLE ELECTRIC FUSE Filod A ril 50, 1921 knife-blade terminals,

thereby, a fuse strip fixed to and carried by.

adapted to Patented Nov. 3, 1925. v

UNITED STATES;

' FRANK 0.1a man, or rrr'rsnunen, rnnnsrnvama.

RENEWABLE ELECTRIC FUSE.

Application filed April 30, 1921. semind. 465,819.

To all whom it may concern:

Be it known that I, FRANK C. LA MAR, a citizen of the United States. residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Renewable lllect-ric Fuses, of which the following is a specification.

This invention relates to renewable or refillable electric fuses of the cartridge or inclosed type.

The object of the invention is to provide a renewable or refillable fuse preferably of the knife-blade type, of simple, economical and eiiicient construction, and which may readily be assembled and as readily disassembled when blown, for the removal of the blown or ruptured fuse element or strip, and refilling or reloading the fuse with a new fuse element.

Another and important object of the invention', is to provide a cartridge fuse of this yp and particularly those parts constituting the locking means for securing the end caps or other removable devices for closing the ends of the shell or casing, are protected from the molten metal of the burned fuse which is carried toward the ends of the casing by the gases created within the casing by the explosion of the fuse, in seeking their escape at the ends of the casing, thereby preventing such molten metal from finding its way between the parts and effectively soldering or forming a union between such parts and locking them together in such a way that the removal by hand manipulation of the end caps or closures is rendered diflicult and impossible, and making it necessary to employ a vise and a wrench or other tools to remove the end closures for disassembling the fuse for reloading.

The invention consists, in a refillable or renewable'f'use, comprising a casing or shell of insulating material, metallic ferrules permanently fixed upon the and disks carried said knife-blade terminals and disks, and screw threads on one or more of said disks and ferrules, said knife-blade terminals and their attached disks and said fuse element be assembled in a unitary struc-. ture and fitted in said casing and screwed to place. 1

in which the metallic parts of the fuse ends of the casing,-

"mit the turning of the The invention further consists in a refillable fuse comprising a shell or casing of insulating material having means for positioning a fuse element therein, end closures for the shell or casing, and disks of fibre or other refractory and non-metallic material fitted upon and carried by said fuse positioning means, and covering said endclosures upon the interior of the shell, all substantially as I will proceed now'more particularly to set forth and finally claim.

In the accompanying drawings illustrating the invention, in the several views of which like parts are similarly designated,

Figure 1 is a side elevation of the fuse. Fig,

2 is a vertical longitudinal section. 'Fig. 3 is aplan or elevation of the knife-blade terminals, end caps or closures and fuse strip in assembled condition. Fig. 4 is a longitudinal section of a modified form of fuse, and Fig. 5 is a longitudinal section of another modified form of fuse.

In the drawings, 1 is the shell or casing of fibre or other suitable insulating and re- ,fractory material. 2and3 are metallic ferrules, preferably of brass, permanently fixed uponthe ends of the shell or casing by means of pins t.

As shown in Fig. 2, the ferrule 2 is provided with an inwardly projecting thickened portion 5 to reduce the opening at the outer end of the ferrule to a diameter slightly less" than the interior diameter of the opening in the shell or casing, and affording a shoulder or stop 6 within the ferrule to abut against the end of the shell or casing when assembling the parts. The thickened portion 5 of the ferrule is provided with an interior screw thread 7 for a purpose presently appearing. I

.The ferrule 3 on the opposite end of the shell or casing is also provided with an inwardly extended thickened portion at its outer end, as at 8, to provide a bore therein of a diameter coinciding with the interior diameter of the shell or casing, and said thickened portion is reduced at its outer edge and provided with a screw thread 9, to receive a screw-threaded clamping ring 10.

having .an inwardly extending annular flange 11 surrounding an annular opening 11 in the end f the clamping ring to perclamping ring about the knife-blade in screwing the ring to place.

The shell or casing as thus constructed.

is adapted to receive the fuse carrying and supporting elements as illustrated in Fig." 2,

and shown in detail and in assembledcondition or as a unitary assemblage in Fig. 3, ready forassembling in the shell or casing.

As shown in Figs. 2 and 3 the fuse carrier or supporting device comprises the end terminals or contacts 12 and 13, herein shown as of the ordinary knife-blade type, having the fiat reduced shanks or terminals 14 and 15 respectively, to which the fuse strip 16 is removably connected at its ends in any usual or suitable manner, as by bolts 17 and nuts 18. r

Mounted upon the shank 14; of the terminal blade 12 or constructed integrally there with and adjacent to and engaging the terminal blade 12, is an' annular disk or plug of metal 19 having its outer or forward end screw-threaded, as at 20, and at its inner end and adjacent to the screw-threads 20 provided with an annular circumferential groove or depression 21 for a purpose presently appearing. or plug 19 is of a slightly less diameter than the bore of the ferrule 3 to permit it to be inserted in the end of the shell carrying the ferrule 3 and slid through the casing and screwed into the interior screw-threads 7 of the ferrule 2 at the opposite end of the shell or casing to form a closure for that end of the shell or casing.

Mounted upon the shank 15 of the terminal blade 13 and abutting against the blade 13, or constructed integrally with these parts, is a disk or plug of metal 22 having a smooth or unt-hreaded periphery, and of I a diameter to fit loosely but closely and snugly in the bore of the ferrule 3, to form a closure for this end ofthe shell or casing, and engaging a shoulder 9 formed on the. interior of the ferrule 3.

In assembling the fuse as thus constructed, the ring 10 having been removed from the end of the shell or casing, the fuse strip and its carrying and supporting terminals or parts having been assembled in a unitary structure as shown in Fig. 3, the leading end thereof carrying the screw-threaded plug or disk 19 is placed in the end of the casing carrying the ferrule 3 and passed through the shell until the. terminal blade 12 emerges from the opposite end of the casing and the casing grasped by one handand with the other hand the terminal blade 12 may be graspedand turned in a counter- -'clockwise direction or the shell or casing turned in a clockwise direction and the terminal blade held stationary and the plug or disc 19- screwed to place within the ferrule 2 thus forming a closure or seal for this end of the casing, and the disk or plug 22 drawn into the ferrule 3 at the opposite end of the shell or casing to form a closure or seal for that end of the shell The screw-threaded disk" or casing,- and then the ring 10 placed over the terminal blade 13 upon the threaded end of the ferrule 3"with its flange l1 engaging the end. of the ferrule and the disk 22 and effectually sealing the joint between said disk against a too free escape of gases and 'prodnets of combustion at this end of the fuse, and securely locking the parts in place.

As shown in Fig. 4 the shell or casing is provided with interiorly screw-threaded ferrules 2, 2, at both ends, and exteriorly screw-threaded plugs. or disks 19, 19", substantially similar to the plug at. the left of Fig. 2 are fixed upon the knife-blade terminals or fuse-strip carrier or support, and in this arrangen'ient, the threaded portions of the ferrule and the plug or disk at the right are of slightly larger diameter'than the corresponding parts at the left, so that the plug at the left may freely pass through the ferrule at the right, in assembling the fuse, and forced through the shell or casing, and by grasping the shell in one hand and turning the knife-blade terminal at the right, the fuse carrier may be screwed to place in the endferrules, the disks or plugs serving as closures or seals for the ends of the casing. In this form of the device the fuse stri 16 is bridged by a bar or strip 23.0f fibre or other suitable insulating and refractory material secured to the opposite sides-of the shanks 14 and 15 of the terminals by the shanks. and thus affording a rigid connection and screwed.

and ferrule between the fuse strip carrying terminals to prevent twisting of the fuse-strip when turnlng or screwingthe fuse and its carrier to I place.

In Fig. 5 the construction is substantially similar to that shown in Figs. 2 and 3', excepting thatthe projecting threaded portion of ferrule 2 on the left-hand side is considerably less than in Figs. 2 and 3 so that in assembling the fuse, thethreads of plug 19 will project beyond the ferrule to receive a clamping ring lOsimilar to the clampingring at the'opposite end of the fuse, as in Fig 2, and in said Fig. 5. This form of the fuse is assembled in the same manneras the assemblage of the-fuse of Fig. 2, excepting the final step of applying the clamping ring at the left hand end.

In order'to prevent the accumulation of molten metal due to the blowing or burning of'the fuse strip upon the occurrence of short ,circuit'ior overload, at the ends of the llO' fuse in and about the screw-threaded connections between the ferrules and the closures or plugs, and which it has been found in effect solders or forms a tight union between the parts of fuses of this sort and renders them difiicult to disassemble without the use j of tools, I provide washers. or

disks 24,01? fibre or other suitable insulating and refractory material, fixed or mounted upon the shanks 14 and 15 .of the end terminals and lying closely a ainstthe closure disks or plugs and of Sue fit closely and tightly the interior diameter I of the end ferrules but permitting the escape of the gases: at the ends of the fuse and effectively checking the passing of the molten particles of metal of the burned fuse therebeyond and into and between the screwthreaded or other adjacent parts of the end closures and thereby avoiding the sticking or soldering of the parts against ready disassembla e by hand. It has been found that the meta ic particles of the burned fuse -will not stick or adhere to the fibre wash ers when a fuse is blown, but merel fall back into the casing, in a loose con ition, and are readil emptied from the casing when the fuse is isasembled for reloading. vThe assembling of the fuse and the dis assembling thereof for reloading will readily be understood from the drawin and the-above description, and further escription thereof is deemed unnecessary.

Whena fuse of the description herein,is blown or ru tured by 'a short circuit or overload in t ecircuit in which the fuse is connected, the gases created by the explosionor burning of the fuse strip will escape past the washers 24 and the disks 22 and at the ends of the fuse provided with the screwthreaded connections, the gases after passing the washers 24 will enter the annular grooves 21 in the screw-threaded plugs or'disks', which grooves afford an expansion chamber or channel for the gases,

and from which the gases will find their 5 of the drawings, the disks 22 fixed to the escape through the'screw-threaded connectionbetween the plugs and ferrules, tothe atmosphere.

In the construction shown in Figs. 2 and terminals 13 have a loose fit or are ca able of a slightrotary movement in the en ferrules, while the lugs or closures at the opposite ends are in rigid engagement with v the ferrules, and by this arrangement it will be observed that should the spring contacts on the switch block or support to V which the fuses are applied be .out of aline ment, and which is quite frequently found to be Ithecase, the, knife-blade terminal 13 carrying. the smoother plain disk 22, in ap-" plying the fuse torthe switchblock or support, will automatically aline itself 'with or compensatefor the non-alinin spring clips or contacts on the switch bloc and thereby avoid skewing of the knife-blade-with' relation to the spring contacts and producing sparking ga s between the blade and contacts,-and e ecting good and ositive contact betw the entire width of t e blade between.

I mnd contacts and avoiding sparking therediameter as to 1 What 1 Gem a 1-. A renewable cartridge fuse, comprising a tubular casing of insulating material, metallic ferrules permanently fixed on the ends of said casing, and a fuse-strip carrierv adapted to he slipped endwise into said casing' and secured in said casing by screwthreaded engagement between the ferrules and said fuse-strip carrier upon relative r0-. tation between the casing and its attached ferrules and the fuse-strip carrier.

2. A renewable cartridge fuse, comprising a tubular casing of insulating material, me-' tallic ferrules permanently fixed on the ends of the casing, and a fuse-strip carriefcomprising endterminals to which said fusestrip is connected and plugs mounted upon said terminals, said fuse carrier adapted to be slip ed endwise into said casing and "secured tlierein by screw-threaded engagement between the ferrules and said plugs upon relative rotation between the casing and said fuse-strip carrier, said plugs serving as 010- sures for the ends of the casing. I

3. A renewable cartridge fuse; comprising a tubular casing of insulating material, metallic ferrules ,permenently fixed on the ends of the casing, and a/fuse-strip carrier relative rotation betw en the casmg and-said fuse-stripcarrien'sai plugs serving as closuresfor the ends of the caslng, and nonbetween the ferrulesl and said'lplugs upon I metallic washers mounted upon said terminals adjacent to the inner sides of said plugs I and fitting closely in said ferrules.

4. A renewable electric fuse, comprising.

a tubular casing of insulating material, an interiorly screw-threaded ferrule permanently fixed to one end of said casing, an;

exteriorly screw-threaded ferrule" permanently fixed tothe other end of said casing and. having an internal diameter slightly.-

greater than the interiorl screw-threaded errule at the opposite en of the casing, a

fuse-strip carrier comprising end terminals, an exteriorly screwthreaded plu mo lmteded on the other terminal, and a fuse-strip on one of saidterminals, a plam disk mountconnected at its ends to said terminals, the

said fuse-strip carrier adapted to be slipped endwise into said casing with its externally screw-threaded plug in engagement with the internally screw-threaded ferrule on the end of the casing and adapted to be screwed thereinto by relative rotation between the casin and fuse-strip carrier and drawing the p ain diskin theopplosite end of the casing thereby closing b0 ends of the easmg, anda clamping ring adapted to be screwed upon the exterior y threaded ferrule on the end of the casing and engaging said plain disk.

5. A renewableelectrio fuse, comprising a vtubular casing of insulating material having a fixed interior screw-thread,.and a fusestr1p carrier, comprising endtermlnals to "which the fuse-strip is connected at its ends,

screw-threads thereon, to afford an expan-J and plugs fixed to said terminals, the said fuse-strip carrier adapted to be inserted endwiseinto said casing and secured thereinby screw-threaded engagement with the caslng upon relative rotation between said casing and fuse-strip carrier, and said plugs serving as closures for the ends of the casing.

.6. A renewable electric fuse, comprising.

a" tubular casing of insulating material, an

internally threaded ferrule fixed to the end of the casing, and .a fuse-strip carrier, comprising end terminals to whlch the fuse-strip is connected at its ends, and an exteriorly' screw-threaded plug fixed to one of said terminals, the said fuse-strip carrier adapted tobe slipped endwise intosaid casmg and secured therein by screw-threaded engagement between said ferrule and plug, said plug affording a closure for the end of the casing, and said plug having an annular groove at its inner end adjacent to the sion chamber for gases escaping through the screw-threadedconnection at the end of said v casing.

7. A renewablelelectric fuse, comprising av tubular casing having a fixed lnterior screwthread at one end, and a fuse-strip car- .rier comprising knife-blade terminals to which a flexible fuse-strip is connected at its ends, disks carried by said termigals, one of ed in said threaded ferrule fixed to the endcof the cas-' said disks having a screw-threaded portion adapted to engage the interiorly screwthreaded end of said casing by relative rot-ation between said casing and fuse stri carrier, and the other of said disks tting loosely in the opposite end of said casing whereby the knife-blade terminal fixed thereto will automatically aline itself with *8. In a renewable electric fuse, a casing of insulating material, a fuse element mounted in said casing, a screw-threaded ferrule fixed to the end of said casing and provided with an interior inte ral inwardly projecting shoulder intermediate the ends of the ferv the springcontacts of a switch block or base.

rule, a disk for supporting said fuse element.

ing and provided with an integral interior inwardly projecting shoulder intermediate the ends of the ferrule, a disk for supporting said fuse element in the casing fitted in said ferrule and adapted to seat against said shoulder and projecting slightly be-' yond. the end of'the ferrule, and an internally screw-threaded cap fitted upon said" ferrule and adaptedto engage saiddisk to hold it in engagement with said shoulder.

I have hereunto set my hand this 22 day of April 1921 at Pittsburgh, Pa. i

' FRANK 0. LA 

